Reason is called common sense to distinguish it from ratiocination with uses logic and rational reasoning.
For the other half he falls back on ratiocination.
In formal logic the drawing of inferences is frequently called ratiocination.
He went too far and fast for even such a Federalist disbeliever in democracy as Gouverneur Morris; who, to Hamilton's assertion that democracy must be cast out to save the country, replied that " such necessity cannot be shown by a political ratiocination.
The detective was very good at ratiocination since he could use logic to figure out how the crime was committed.